The utility of many therapeutics, particularly biologicals such as peptides, polypeptides and polynucleotides, suffer from inadequate serum half-lives. This necessitates the administration of such therapeutics at high frequencies and/or higher doses, or the use of sustained release formulations, in order to maintain the serum levels necessary for therapeutic effects. Frequent systemic administration of drugs is associated with considerable negative side effects. For example, frequent systemic injections represent a considerable discomfort to the subject, and pose a high risk of administration related infections, and may require hospitalization or frequent visits to the hospital, in particular when the therapeutic is to be administered intravenously. Moreover, in long term treatments daily intravenous injections can also lead to considerable side effects of tissue scarring and vascular pathologies caused by the repeated puncturing of vessels. Similar problems are known for all frequent systemic administrations of therapeutics, such as, for example, the administration of insulin to diabetics, or interferon drugs in patients suffering from multiple sclerosis. All these factors lead to a decrease in patient compliance and increased costs for the health system.
One method for increasing the serum half-life of a protein is to attach it to a pharmacokinetic moiety. One type of pharmacokinetic moiety that has been used is an “Fc” domain of an antibody. Antibodies comprise two functionally independent parts, a variable domain known as “Fab”, which binds antigen, and a constant domain known as “Fc”, which links to such effector functions as complement activation and attack by phagocytic cells. An Fc domain has a long serum half-life. Capon et at. (1989), Nature 337: 525-31. When fused to a therapeutic protein, an Fc domain can provide longer half-life or incorporate such functions as Fc receptor binding, protein A binding, complement fixation and perhaps even placental transfer.
This application provides novel Fc fusion proteins that increase the serum half-life of various therapeutics, polypeptides having increased serum half-life, and methods for increasing the serum half-life of therapeutics.